In the past, computing applications such as computer games and multimedia applications used controls to allow users to manipulate game characters or other aspects of an application. Typically such controls are input using, for example, controllers, remotes, keyboards, mice, or the like. More recently, computer games and multimedia applications have begun employing cameras and software gesture recognition engines to provide a human computer interface (“HCI”) or natural user interface (“NUI”). With HCI or NUI, user motions are detected, and some motions or poses represent gestures which are used to control game characters (e.g., a user's avatar) or other aspects of a multimedia application.
In a natural user interface, an image capture device captures images of the user's motions in its field of view. The field of view can be represented as a finite Euclidean three-dimensional (3-D) space. A user can be performing a gesture with a body part but the user also tends to move around in the field of view of the capture device. A person extending her arm as a gesture while dancing about the room will generate a motion trajectory that will require more processing to decouple the arm action from the effect of the dancing motion. Additionally, users perform gestures at different speeds, providing another factor for which to account in gesture determination. Furthermore, the gesture recognition and subsequent responsive action need to be done in real-time and processed within the frame rate of the NUI system.